Drying apparatus



T. G. JOHNSON DRYING APPARATUS Filed Nov. 24. 1930 2 Sheets-Sheet leniog July 11% 1934. JOHNSON 1,966,629

DRYING APPARATUS Filed Nov. 24. 1930 2 Sheets-Sheet 2 14 f Ifjflijfiilllllll'jjj 'LQIE: I,ZII :Z 11' 1::

Patented July 17, 1 934,

DRYING APPARATUS Thomas G. Johnson, Cloquet, assignor to The NorthwestPaper Company, Oloquet, Minn, a corporation of Minnesota ApplicationNovember 24. 1930, Serial No. 497,102 3 Claims. ((31. 34-43) The presentinvention relates to dryers, espe- Fig. 1 is a diagrammatic view inelevation of cially for paper machines. 4 a section of. a paper machine.

Between drum dryers of paper making ma- Fig. 2 is a diagrammatic view ofthe air feedchines, particularly in those portions where ing system ofthe invention.

5 fabric, known asa felt, travels with the paper, Fig. 3 is an end viewof the paper machine there are formed elongated pockets of rathersection of Fig. 1 showing also an end view of the limitedcross-sectional area between the felt and air-feeding system. the paperand rolls. Both the felt and the paper One feature of the invention isthe use of are thus exposed for evaporation of water or warm, waste air.It is well known that the ca- 10 moisture. Because of the elongated andsome pacity of air to absorb moisture is greater, the times tubularnature of these pockets the normal higher its temperature. This isreadily illustrated circulation of air is poor and drying is irregularfrom the data of the following table:

and not uniform across the widths of the felt and of the paper web. Thisresults in uneven Table 1 tension in both felt and web. The unequalizedconditions of drying in both cases affect the Gmms uniformity of qualityin the paper. ,They also Temperature Increased afiect the life of thefelt and render it non-unie meter capaclty of saturated per 10 C. formin character across its width because-oi air 20 continued use withdifierent degrees of moisture 7 The present invention aims to increasethe 9.3717 4-4954 20 17.1768 7.8051 rate of evaporatlon of a paperdrying machme 30 301293 129525 and to render the drying more uniformalong the 25 width of the paper web and the felt. Another object is toprolong the life of the In the e w I am to utmze Waste felts byuniformly decreasing the moisture con warm, moist 8.11 which may becollectedfrom tent thereof in use. around the paper machine. rather thancooler Still another object of theinvention is to ina dryer r i befiaken m i 30 crease the production of a paper machine ooca- 0 5 and tus Its b moisture. The air wasted from sioned by the miproved drying.paclty to absor A further object of the invention is the provithepockets 0f the machme W111 be at high temperature and may be near thetemperature of .sipn of means to admit q p air steam. All the heat unitsin this wasted air may mto the pockets, to adm1t the air with a gentlebe considered as lost in ordinary practice flow, and to use warm, wasteair from around the In this invention I remse much of this paper machinewhich air is further heated to mand hence fi t a saving in heat unitsAlthough crease its moistu absorbing y- I use preheated air, it is sogently introduced is particular Object 0f the invention to that itbecomes further heated in the pockets admit the air into the poc inSuCharegulated and thereby has its capacity to hold moisture 40 manner thatthe air discharged from'the pockets further increased.

'is substantially saturated at the temperature of In consequence Iattempt to regulate th t discharge, ther by approaching h al fmaXiperature, the moisture and the rate of use, so mum efficiency in theuse of heat units. that the air discharged from the pockets is sub- 45Various other Objects and advantages offiihe stantially saturated.

invention are co p and Will be pparent The air which leaves the ends ofthe pockets from the following description of the invention circulatesand mingles with air circulating as it is applied to a known type ofpaper mathrough the machine. A good portion of this chine, shown in theaccompanying drawings, in air usually leaves directly through hoodsproso which: vided to carry ofi the moist air and the rest of 10 itmingles with the air in the room. A portion drops into the pit under themachine.

In the accompanying drawings I have illustrated a paper machine bytaking one section thereof as typical of the several features of thepresent invention, and it will be readily understood how the entiremachine may embody duplicating parts of the invention.

A length of machine is selected at the center of which there is adivision into forward and rearward drying sections. The importantdistinction appearing herein is the use of different felts for the twosections. There are one series of drying rolls 10 in one section andanother series 11 in the other section. The frame of the machine isomitted in order to make clearer the constructions involving theinvention.

The upper rolls of the series 10 have a felt 12 which holds a paper web13 to the rolls, the lower stretch of the felt being looped over idlers14 between the rolls. An upper stretch 15 on idlers 16 completes theendless loop of felt 12. The lower rolls of series 10 have a similarlyarranged endless felt 17, idlers 18 between the rolls, a return stretch19 and idlers 20 therefor. The other series of rolls 11 has a similarconstruction with upper felt '21 and lower felt 22.

The felts, the web and the rolls and the idlers all combine in variousways to form long or tubular pockets. Ordinarily the air stagnateslocally in the pockets and is hot and saturated.

This reduces the effective drying area, delays the completion of theprocess, and causes non-uniform drying across the width of sheets. Intothe pockets I project air lines, at various and adjustable depths in thepocket, and I provide ineans for supplying pre-conditioned air to saidmes.

As a source of air I prefer the warm moist air found in the machine pit.Beneath the level of the lower rolls 10 and 11 and above the floor 23,at one side of the machine is a flared air intake 24 (Figs. 2 and 3)connected by an elbow 25 to a.v blower 26, operated by pulley 27. Aconduit leaves the blower and branches out to various parts of themachine. It comprises a riser 28 extending to a point above the rolls 10and 11, parallel feeders 29 and 30 along the two sides of the machine, across-connection 31 in one feeder, a T-connection 32 in the otherfeeder, a connecting length 33 from the cross-connection to theT-connection, and a horizontal feeder 34 from the cross-connection tothe riser.

Means is provided to heat the air and I prefer to use lengths of steampipe'within the overhead air feeding system. I provide a single steamline throughout the whole feeding system. A valved steam line 35 entersthe overhead system and follows the branches'as indicated by dottedlines and arrows in Fig. 2 returning parallel to itself in each part ofthe conduit system. It emerges at 36 and at the end is provided with asteam trap 3'7. -By this system air can be heated quickly without thenecessity of circulation, or forcing heated air from one place toanother. Hot air is on tap.

From each length of feeders 29 and 30 are depending valved lengths ofpipe 38 tapped into the feeders, as shown in Figs. 1 and 3. Some extendto the level of the lower pockets. Others extend only to certain highpockets, such as lengths designated 40 and 41. The nozzles may be placedat any location where they are desirable, and this may be variedaccording to conditions.

Ordinarily, a large number are provided and are operated as conditionsmay require. Each one has a length of pipe 43 entering a pocket to apoint where it is particularly desirable to increase the drying. Theremay be either one or two in a pocket, and one or both may be operated. Iprefer to make the horizontal length 43 adjustable, either by utilizingdifferent lengths of pipe, or by using a telescoping constructionwhereby one pipe 44 slips over pipe 43.

In order to protect the paper and the felt from injury by dirtaccidentally emerging from the air-system, I may provide a screen filter45 on the ends of the pipes.

In operation of the system air is gently introduced from the air systeminto the pockets. High pressure is not employed. Only suflicient air isrequired to insure circulation of air through the pockets. The normalcondition of the air in the pockets is one of practical saturation andhigh temperature. The normal condition of air in the air system may bemoist but not saturated at an elevated temperature which may be lower'than the temperature of air in the pockets. This heated moistnon-saturated air replaces the saturated air and itself approachessubstantial saturation as'it leaves the pocket.

One feature of the invention is the use of heated, waste, non-saturatedair at an elevated temperature to induce circulation through the pocketsand to induce uniform drying in pockets. Very little heat is required topreheat the air in the system as compared with air taken fromout-of-doors. Because the air is heated and later becomes practicallysaturated, there results a higher efiiciency in use of heat units inoperating the paper machine.

The invention permits an operator to observe the paper and felts andwhere he finds a region drying slower than other regions, he mayincrease or localize the supply of air to cure the difiiculty. Byproviding the valved lines 38 and telescopic lengths, adjustments may bemade for peculiarities of machines and conditions of operation.

I have found that with the system here described I have been able tooperate the drying drums at a steam pressure of five pounds per sq. in.as compared to a pressure of eighteen pounds which is otherwisenecessary. In addition to this reduction in temperature of the dryers Ihave been' able to increase production of the machine 10%, produce apaper of uniformly high moisture content, a paper which is evenly driedacross the machine, and have been able to more than double the life ofthe dryer felts.

I claim:

1. A drying system for a paper making machine comprising in combinationwith a papermaking machine having pockets therein, a source of warmwaste air, an air distributing conduit extending along the length of themachine, means to collect. and force said air through said conduit, asteam line coextensive with said conduit to heat the air therein, anddischarge lines connected with said conduit for discharge ofthe heatedair into pockets of the paper machine.

2. Adrying device for a paper making machine comprising in combinationwith a paper-making machine having an elongated; pocket therein formedby rolls and travelling sheets, an air-discharge line projecting at adepth into said pocket, said line having a telescopic structurepermitting placement of the inner end of said line at a predeterminedregion in the pocket, and means to supply a drying air o said line.

aeaeae therefrom, means coextensive with said conduit to heat andmaintain hot the air in said conduit, and a series of discharge pipelines from said feeder conduit each extending to a depth into thepockets of the paper machine.

THOMAS G. JOHNSON.

